Apparatus for metal spray molds



May 9, 1961 M. BRUCKER 2,982,996 APPARATUS FOR METAL SPRAY MOLDS 'O'riginal Filed May 22. 1953 3 Sheets-Sheet l MILTON BRUCKER,

' INVENTOR.

ATTORNEYS May 9, 1961 M. BRUCKER APPARATUS FOR METAL SPRAY MOLDS 5 Sheets-Sheet 2 @riginal Filed May 22, 1953 FIG.7

MILTON BRUCKER,

INVENTOR.

ATTORNEYS y 1961 M. BRUCKER 2,982,996

APPARATUS FOR METAL SPRAY MOLDS Qriginal Filed May 22, 1953 3 Sheets-Sheet 3 FIG. 8

MIL TON BRUCKER.

INVENTOR.

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ATTORNEYS Patented May 8, 1961 2,982,996 I APPARATUS FOR METAL SPRAY MOLDS Milton Brucker, Los Angeles, Calif., assignor, by mesne assignments, to Zenith Plastics Company, Gardena, Calif., a corporation of Delaware Original application May 22, 1953, Ser. No. 356,759,

now Patent No. 2,879,196, dated Mar. 24, 1959. Divided and this application Feb. 2, 1959, Ser. No.

9 Claims. (01. 18-35) This invention relates to production molds of a. metal spray type, and more particularly relates to a new and improved construction thereof.

This application is a division of my copending application Serial No. 356,759, filed May 22, 1953, now US. Patent No. 2,879,196, granted March 24, 1959.

It is among the objects of this invention to provide a new and improved metal sprayed mold associated with the means for drawing a vacuum simultaneously upon a molding surface and also upon a back surface of the mold, thereby avoiding vacuum leakage through the mold body and avoiding undesired bubbling and pitting of the molded parts, particularly the surface adjacent the mold surface. i

It has been found in metail sprayed molds. of the desired character described that the mold body of sprayed material is, to some extent, porous, so that when a vacuum is drawn so as to evacuate air betweena readily yieldable bag in accordance with conventional practice, undesired pitting, blistering, and other malformation of the surface of the molded parts results. It tis found that by applying a vacuum to the outer side of the sprayed" met-a1 mold, such undesired permeability of the sprayed metal of the mold bodyis effectively eliminated as a factor in the molding operation.

It is therefore among the objects of this invention to provide a new and improved apparatus to take advantage of the above-stated discovery as to provide a more uniformly superior molded product.

It is. another object of the invention to provide a new and improved means associated'with Iametal' sprayed mold, for drawing a vacuum thereon in a vacuum bag type molding operation. 9

Itis also among the objects of the invention to provide improvements over the prior artapparatus heretofore intended to accomplish generally similar purposes, to improve the vacuum distribution over an enlarged surface area of relatively large parts being molded, and to provide new and improved means for achieving such wide distribution of vacuum so a's to obtain a superior molded P With these and other objects in view, the invention consists of the construction, arrangement and combination of the various parts of the device whereby the objects contemplated are attained,. as hereinafter set forth, pointed out in the. appended claims, and illustrated in the accompanying drawings. 7 p

In the drawings: v Figures 1 through 5 are vertical sectional views'illustrating the steps offorming a mold of the character'most pertinent to the practice of this' invention. v I

Figure 6 is an elevational'view of aic'ompleted m'old' asused, parts being cutaway. t

Figure 7 is a top view ofthmold of Figure 6." Figure 8 is a fragmentary verti '"Figure9 is a similarly enlarged ve'ftic'al sectional 'view sectional'view, en larged t'aken as "on. a line 8- 8 nf Figure 7;

thatthe cavity '27 formerlyoccu'pied by the wax defiiies desired die or mold and an integral base 22 defining an I annular flange.

After the plaster mold 20 has been shaped to the desired configuration, the outer surface is sanded and finished to a smooth condition. A light coating 23 of zinc or'the like. metal is then flash-sprayed over the outer surface of the plaster mold, including the upper surfaces thereof, and the upper flange surface 24 of the base 22.

Next a layer of bronze is sprayed over the zinc to a thickness of approximately one-eighth to one-quarter inch, as designated at 25in Figure 2. The bronze coating provides a hard surfaced layer for the interior of the final mold, as willbe seen. 7

Over the outer surface of the bronze coat, a coat of aluminum or the like metal 'is'applied so as to give a good bond between the bronze and a resin 'to be applied over the aluminum. Such aluminum coating is also deposited, preferably by spraying, as stated, to athickness of approximately one-quarter to one-half an inch. This aluminum coating 29 eventually provides one of the layers of the porous metal body. shell 58 (Fig. 8) of the completed mold as will appear hereinafter.

A coating of wax or paraflin is next deposited, as in a continuous sheet, by daubing, brushing, spraying, or otherwise, over a substantial portion of the surface of the aluminum. For. this purpose the aluminum may be formed with ashoulder, as .at 26, formed from a thick. ened peripheral rim around the perimeter thereof pro,- vided on theside of the metal shell 58 opposite the mold surface 35 (Fig. 8) of the shell, providing a recess, as at 27, for said wax coating 28 over the corresponding major portion of the mold. Said wax 28 is preferably deposited to a thickness of approximately one-eighth of an. inch, although the thickness of the wax layer 28, like thethicknesses of the bronze and aluminum layers, 25 and 29, may vary Within limits which are readily apparent from a consideration of the-particular. use to which the mold. is to be put, its size, and the like considerations. 1

Over the aluminum coat 29, including the shoulder area 26 and also continuously over the wax coat 28, a. plurality of layers of laminate, preferably of glass; cloth, or other reinforcement,. impregnated with a suitable resin, such as a polyester, is laid, in intimate contact with said wax and aluminum portions. The resultant mold, with such laminate 30 impregnated with said resin, is then heated to a sufficient temperature, say F., to

cure the reinforcing resin. And in orderto insure that such resin'cures, preferably at a temperature lower than.

themelting point of the wax, the resin may be hopped up with suitable accelerators or thelike.

After the resin 30 has set so as to providea firm back- 1 the wax to be withdrawn, preferablyunder-vacuum, so

a hollow chamber or space separating, at'leastiover stantialportior'i or itsare'a, the'reinfo'rcing-lamiiiate 50 and'the sprayedmet-al rnold portion 23, 25 and 29;

[It'is not essential that {the waxbe withdrawfifat' tli I v presentstage of operation. It may subsequently be" 3 withdrawn as during a first molding operation utilizing the completed mold.

A fiberglass laminated cap or edging 31 may be used to reinforce and bind the metal portions of the mold to thelarninatedbacking 30 Appropriate metal reinforcement, such as a pipe 32, is also secured, in any appropriate manner, to the edge 24 of the mold to insure dimensional stability of the mold.

The plaster core 20 is broken out at any convenient stage to expose said zinc metal bond coat 23. The inside of the mold is then sanded or dressed out until all of the zinc layer 23 has been removed, exposing the layer of bronze for use as the inner face of the mold.

In the use of the mold, the same, including said reinforcing frame 32, is mounted as upon a suitable structure 33, including castors, or the like, 34, to facilitate transport.

In a typical use, a layer of parting agent is applied to the interior surface 35 of the mold, and then a number of layers 36 of resin-impregnated fiberglass cloth are applied thereto. The main body of the part in question is given thickness, strength and rigidity by a layer of fiberglass cloth honeycomb 37. The upper edges of the mold are built up to a thickness corresponding to that of the honeycomb as by a plurality of layers of fiberglass laminate 38 extending to the top edge 39 of the mold. Another plurality of layers of fiberglass cloth similarly impregnated with resin is applied thereto as at 40, and over the latter, preferably a layer of cellophane, or its like, 41, is applied.

A layer of industrial mat 42 may be applied as in strips, as shown most clearly in Figures 7, 8 and 9, over another preferably continuous layer 43 of such industrial mat comprising, e.g., an unimpregnated fiberglass material. Said strips 42. comprise bleeder strips which terminate, as at 44, at the upper edge of the mold where a conduit 45 is formed around the upper mold edge circumferentially thereof, most advantageously by means of a wire coil of helical spring shape, the individual coils being in spaced relationship from one another, to permit the free passage of air therebetween.

Over the above assemblage a vacuum bag 46 is applied, said bag being preferably of a material such as vinyl alcohol, which is secured in air-tight fashion around the circumferential periphery 47 of the mold, by.a suitable seal, such as zinc chromate putty 48.

' The upper rim 49 of the mold is drilled, as at 50, and tapped, as at 51 for the threaded accommodation of a metal tubing 52 which. makes connection with a similar tubing or pipe 53, similarly drilled and tapped into the bottom of the mold, but only through the resin-reinforced layers 30, so that such tubing 53 communicates inwardly with the wax-formed recess 27.

' Suitable conduits S4 interconnect the pipes and tubes 52, 53 and 54 to a source of vacuum, not shown, by means of a hose or the like 55, in which a resin trap 56 is also connected. A plurality of such resin traps 56 may be employed, and it is also preferable to provide a plurality of such metal tubing, nipples, or the like, 52, at spaced intervals around the upper edge of the mold.

When a vacuum isdrawn through the hose 55, and the several conduits 52, 53 and 54, the poly-vinyl bag 46 is drawn firmly against the underlying bleeder strips 42, the-layer of fiberglass mat 43, and the upper portions of the coil spring conduit 45. Said nipples 52 are in direct communication through their respective bores 50 with said coil spring conduit 45 so that air is drawn uniformly from the interior of the mold between the bag 46 and'the metal moldportion 58. t

Previously, that is, without the space 27 and nipple 53, or the like, which serves to draw a .vacuum upon the outer side of the metal shell 58, it has been found that theporosity of the metal158 causes an, ir nperfect surface to form at 35, due to pitting and bubbling occasioned by penetration of air from the metal 58 into the molded parts.

However, by the instant provision of a space, such as 27, between the resin-laminated backing 30 and said metal shell 58, any air pressure exerted upon the metal 58, and which would otherwise cause leakage into the molded part is neutralized by the vacuum simultaneously drawn in the space 27. The molded part is thus formed and cured in the mold without surface blemishes, pockmarks, and the like imperfections due to said undesirable air leakage.

The thickness and rigidity of the metal shell 58 are sufficient, as is the body of the reinforcing laminate 30, to maintain the air space 27 in an effectively unconstricted condition when a vacuum of approximately 18 to 20 inches of mercury is drawn.

The above principles, while illustrated in connection with a female mold, are equally applicable to male molds and may likewise be utilized in the fabrication of any intermediate or varied structure, even including flat parts, or parts which are partially convex and partially concave.

By the use of the coil spring type conduit, vacuum is drawn equally upon all parts of the upper edge and periphery of the molded and laminated parts, thereby materially assisting the removal of air from between the plies of the laminate, as well as beneath the bag 46 to exert any desired pressure upon the parts to be molded. These considerations are advantageous in the instant apparatus and method, so as to materially assist the drawing of a uniform vacuum on the molded part and on the inner and outer walls of the mold through the space 27, or its like.

The above described apparatus and the method also described above are adapted for use in molds of analogous type in order to correct accidentally developed leakages through the body of the mold or in strategic positions or areas of the mold.

Although I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom Within the scope of my invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent means, methods and devices.

I claim:

l. A mold comprising a porous metal shell having an exposed mold surface conforming to the surface geometry of a part to be molded, a reinforcing backing covering the surface of said shell opposite said exposed mold surface, at least a portion of the reinforcing backing covered surface of said shell and said reinforcing backing being spaced from one another and forming a hollow chamber therebetween, and means communicating said chamber with the exterior of said mold whereby a vac uum may be drawn in said chamber simultaneously with the drawing of a vacuum on a molded part positioned against said exposed mold surface of said porous metal body.

2. A mold comprising a porous metal shell having an exposed mold surface conforming to the surface geometry of a part to be molded, a reinforcing backing covering the surface of said shell opposite said exposed mold surface, said reinforcing backing and said porous metal shell having a hollow chamber formed therebetween generally commensurate in area with the useful area of said exposed mold surface of said metal shell, vacuum drawing conduits inter-communicating said chamber and said exposed mold surface with a vacuum drawing source whereby a vacuum may be drawn simultaneously in said chamber :and on a molded 'pa'rt positioned against said mold surface exteriorly of said shell.

3. A mold comprising a porous metal shell. having. an exposed; moldsnrfa'cq conforming to the surface geometry of a part to be molded, a reinforcing backing covering the surface of said shell opposite said exposed mold surface, said reinforcing backing and said porous metal shell having a hollow chamber formed therebetween generally commensurate in area with the useful area of said exposed mold surface of said metal shell, vacuum drawing conduits intercommunicating said chamber and said exposed mold surface with a vacuum drawing source whereby a vacuum may be drawn simultaneously in said chamber and on a molded part positioned against said mold surface exteriorly of said shell, said metal shell being thinner in cross-section in the area thereof forming the shell wall of said chamber than in those areas thereof immediately surrounding said chambet.

4. A mold comprising a porous metal shell having an exposed mold surface conforming to the surface geometry of a part to be molded, a reinforcing backing covering the surface of said shell opposite said exposed mold surface, said shell having a thickened peripheral rim around the perimeter of said mold surface provided on the side of said shell facing said backing and opposite said mold surface, the thickness of said shell wall substantially throughout the area of said mold surface being thinner than that of said peripheral rim, said hacking being joined to the peripheral rim of said shell throughout the periphery of said rim, said thinner shell wall portion and the surface of said backing covering such thinner shell wall portion being spaced from one another and forming a hollow chamber therebetween, and means communicating said chamber with the exterior of said mold whereby a vacuum may be drawn in said chamber.

5. A mold comprising a porous metal body having an internal shape conforming to the desired figuration of a part to be molded therein, said inner surface being noninhibiting metal relative to the curing of a resin to be placed thereagainst, and a reinforcing backing extending over substantially the entire opposite surface of the mold, said reinforcing backing being spaced from a backside of the metal body portion of the mold and providing a hollow space therebetween, and means for drawing a vacuum between said metal mold portion and saidreinforcing backing through said space simultaneously with the drawing of said vacuum on a molded part positioned against the inner surface of the mold on the opposite side of said metal mold portion.

6. A mold as defined in claim 5, said reinforcing backing comprising a laminated resinous body.

7. A mold as defined in claim 5, said space defining a passageway extending over substantially the external surface of the metal body portion of the mold.

8. A mold as defined in claim 5, said metal body portion comprising an inner body of bronze and an outer body of aluminum.

9. A mold as defined in claim 5, said means for drawing said vacuum comprising said mold being formed with a plurality of passageways intercommunicating with a vacuum source, selective of said passageways having intercommunication with one another and with the interior of the molding surface of the mold, said intercommunication comprising a vacuum bag impervious to air, and a coiled wire conduit extending from one to another of said selected passages under said vacuum bag, and means for sealing said vacuum bag to the outer marginal portion of said mold. 1

References Cited in the file of this patent UNITED STATES PATENTS 285,058 Nickerson Sept. 18, 1883 730,102 Dunne June 2, 1903 2,367,779 Hull Jan. 23, 1945 2,376,805 Peacock May 22, 1945 2,380,573 Beasecker July 21, 1945 OTHER REFERENCES Plastics Engineering Handbook (Soc. of the Plastics Ind.), published by Reinhold Publishing 00., New York, pp. 209-211. 

